Prostate cancer is one of the most common cancers in men in the United States, with 186,320 new cases estimated in 2008 and one of the leading causes of cancer death among males with approximately 28,660 deaths estimated in 2008 (see, e.g., Jemal et al., CA Cancer J. Clin., 58: 71-96 (2008)). Despite recent advances in androgen-deprivation therapy and chemotherapy, there is currently no curative treatment for metastatic prostate cancer. Current therapies are unable to completely eliminate androgen-independent prostate cancer cells that remain after androgen ablation (see, e.g., Karnes et al., Curr. Pharm. Des., 12: 807-817 (2006)).
One approach to prostate cancer treatment is specific immunotherapy, either alone or in combination with standard definitive radiation therapy or chemotherapy (see, e.g., Arlen et al., Clin. Cancer Res., 12: 1260-1269 (2006); and Gulley et al., Clin. Cancer Res., 11: 3353-3362 (2005)). In the last few years, immunotherapy employing several different prostate cancer vaccines has shown promising evidence of clinical benefit in various patient populations (see, e.g., Schlom et al., Curr. Oncol., 14: 238-245 (2007); and Harada et al., Int. J. Clin. Oncol., 8: 193-199 (2003)). Tissue-specific antigens, which are expressed in both normal prostate and prostate cancer cells, can be targeted for prostate cancer-specific immunotherapy. Prostate cancer-associated antigens have been identified (see, e.g., Arlen et al., Expert Rev. Vaccines, 2: 483-493 (2003); Ghosh et al., J. Cell Biochem., 91: 528-539 (2004); Iavarone et al., Mol. Cancer. Ther., 1: 329-335 (2002); Jalkut et al., Curr Opin. Urol., 12: 401-406 (2002); Kiessling et al., Int. J. Cancer, 102: 390-397 (2002); Likja et al., Nat. Rev. Cancer, 8: 268-278 (2008); Peshwa et al., Prostate, 36: 129-138 (1998); Slovin et al., Expert Opin. Ther. Targets, 9: 561-570 (2005); Taira et al., Oncology (Williston Park), 21: 1003-1010 (2007); and Yokokawa et al., Int. J. Cancer, 121: 595-605 (2007)). Several of these antigens, however, also are expressed in some normal tissues (see, e.g., Carter et al., Proc. Natl. Acad. Sci. USA, 93: 749-753 (1996); and Reiter et al., Proc. Natl. Acad. Sci. USA, 95: 1735-1740 (1998)).
Therefore, the desire exists for new approaches for the treatment of prostate cancer.